A comparative study of the magnetic and microwave properties of Al3+ and In3+ substituted Mg–Mn ferrites

Abstract The effect of substitution of diamagnetic Al3+ and In3+ ions for partial Fe3+ ions in a spinel lattice on the magnetic and microwave properties of magnesium–manganese (Mg–Mn) ferrites has been studied. Three kinds of Mg–Mn based ferrites with compositions of Mg0.9Mn0.1Fe2O4, Mg0.9Mn0.1Al0.1Fe1.9O4, and Mg0.9Mn0.1In0.1Fe1.9O4 were prepared by the solid-state reaction route. Each mixture of high-purity starting materials (oxide powders) in stoichiometric amounts was calcined at 1100 °C for 4 h, and the debinded green compacts were sintered at 1350 °C for 4 h. XRD examination confirmed that the sintered ferrite samples had a single-phase cubic spinel structure. The incorporation of Al3+ or In3+ ions in place of Fe3+ ions in Mg–Mn ferrites increased the average particle size, decreased the Curie temperature, and resulted in a broader resonance linewidth as compared to un-substituted Mg–Mn ferrites in the X-band. In this study, the In3+ substituted Mg–Mn ferrites exhibited the highest saturation magnetization of 35.7 emu/g, the lowest coercivity of 4.1 Oe, and the highest Q×f value of 1050 GHz at a frequency of 6.5 GHz.